Method of constructing foundations



June 19, 1934. M. F, CLEMENTS ET AL 1,963,351

METHOD OF CONSTRUCTING FOUNDATIONS Filed Aug. 3, 1931 2 Sheets-Sheet 1amnion Mel Ville F'lemezzzs'.

flickii'iie lm era June 19, 1934. M. F. CLEMENTS ET AL METHOD OFCONSTRUCTING FOUNDATIONS Filed Aug. 3, 1931 2 Sheets-Sheet 2 I Ir wywwmwa amnion, filelrz'lle'FClemenis Wick Ffle liner; %1 0L ammqoPatented June 19, 1934 UNITED STATES METHOD OF CONSTRUCTING FOUNDATIONSMelville F. Clements and Nick F. Helmers, St. Paul, Minn.

Application August 3, 1931, Serial No. 554,620

2 Claims.

Our invention relates to improvements in the method of constructingfoundations and is particularly adapted for use in the construction ofsubaqueous foundations which have an extensive horizontal area.

It is the object of our invention to provide for the construction of acaisson of any desired type in multiple sections around a central orenclosed area and thus to facilitate the excavation for and building ofthe foundation in the central area.

It is also our object to'avoid the known difficulties of sinking aunitary or integral caisson of great horizontal dimensions.

Further objects of our invention are to provide a series of smallcaissons which, when joined together, form an outer wall or compositecaisson, enclosing a central area to be excavated and filled; to soarrange the circumferential caissons that they may act as a support foran enclosed central chamber, and to provide a roof cover for thiscentral chamber which will permit the preparing of the foundationbeneath it by the open dredging method or the pneumatic method, or anyother known method.

Referring to the drawings, Figure 1 is a plan View of ourcircumferential caissons and also shows diagrammatically a surroundingcofferdam; Figs. 2, 3 and 4 are vertical sections of caissonsillustrated in Fig. 1 showing various phases in the progress ofconstructing a fo ndation by the method herein described; Fig. 2 showingthe initial step in constructing two of the circumferential caissons;Fig. 3 showing the circumferential caissons sunk to bed rock, prior tothe excavation of the central areas, and with the roof over said area inplace and Fig. 4 illustrates a foundation completed according to ourmethod and supporting the pier 15 of a bridge.

In the drawings, A represents bed rock, B ledge rock or other surfacematerial overlaying the bed rock, C sand, silt or other fine materialand D concrete.

The circumferential caissons of our foundation may be constructed by anyknown method, but we prefer to construct them in the open and upon asand island from within a cofferdam. In carrying out our invention, wefirst build a cofferdam 10 surrounding the entire foundation to beconstructed, as illustrated diagrammatically in Fig. 1; we then pumpdown the water within said cofferdam to a predetermined level of sayfifty feet and fill the interior of the cofferdam with sand or othergranular material to that level to permit building the caissons on aflat surface.

We then build on the island thus formed the first section (see Fig. 2)of caissons 1, 3, 5 and 7 (Fig. 1), and remove the sand and water tosink said sections. By placing a bulkhead 11 approximately seven feetabove the cutting edge 12 of the several caissons, the use of thepneumatic method in completing the sinking of the caissons is madepossible. We continue the building of successive sections of thecaissons 1, 3, 5 and '7 above those already sunk and continue thedredging until the four caissons above designated are down to bed rockon which the foundation is to rest. We then construct and sink in thesame Way caissons 2, 4, 6 and 8. The permanent material 13 to be addedon the interior of each caisson is now placed. The openings 9 betweenthe caissons are then cleaned and the caissons are united to form anintegral wall by bonding them together and filling the openings withconcrete, 9a..

The material in the central space within the wall formed by the caissonsmay now be removed by the open cut method. After this work hasprogressed to a level somewhat above bed rock, a roof 14 (Figs. 3 and4), preferably consisting of a heavy slab of reinforced concrete, isplaced over the central area and supported by the caissons so that thework of excavation may be completed by the pneumatic process.

Thus the chamber formed by the roof and the caissons is supplied withair under pressure to enable workmen in the chamber to excavate thematerial therein without interference from water which, in the absenceof the pneumatic pressure, would find its way into the chamber.

During the construction of the caissons, reinforcing bars 15 areinbedded therein, adapted to project into the spaces- 9 between thecaissons and also into the central area enclosed by the caisson wall.These reinforcing bars may be turned up against the caissons (see Fig.3) during the process of sinking the same so as to reduce slidingresistance, and after the caissons have been sunk to their permanentposition these bars 15 are bent outward to furnish a bond for theconcrete in the spaces between the caissons and also to furnish asimilar bond between the caisson wall and the central area within thewall which we finally fill with concrete to form a well bonded footing.

The utility and desirability of our method of constructing massivefoundations is evident since it has been proposed to construct a pier185 feet by feet in plan and resting on rock feet below the watersurface. The use of a single caisson in the construction of such a pierfoundation is inexpedient, if not impossible, because of cost and theengineering problems involved in fabricating, placing and sinking acaisson of so great dimensions.

Having described our invention, what we claim as new and desire toprotect by Letters Patent is:

1. The method of constructing a foundation below water which consists inmaking and sinking to bed rock a series of circumferential caissons,filling the space between the several caissons and uniting the same toform an impervious outer wall, placing on said wall, above Water, alarge, heavy roof adapted to withstand internal pneumatic pressure,filling the chamber formed by said wall and roof with air under pressuresubstantially above atmospheric pressure and then while maintaining airpressure above atmospheric therein, excavating the material beneath saidroof and then filling the excavation with concrete or other suitablebuilding material, and bonding it to the wall to form a solidfoundation.

2. The method of constructing a foundation of large horizontal extentbelow water which consists in enclosing the entire area to be occupiedby the foundation within a wall comprising a series of circumferentialcaissons, then covering the entire area enclosed by said wall by a roofadapted to withstand pneumatic pressure Within the chamber formed bysaid caissons and roof, filling said chamber with air under pressuresubstantially above atmospheric pressure and then while maintaining airpressure above atmospheric pressure, excavating the material beneathsaid roof and finally filling the excavation to form a solid foundation.

MELVILLE F. CLEMENTS. NICK F. HELMERS.

